Up-to-date motor vehicles, in particular passenger vehicles, are generally equipped with hydraulic or electrohydraulic servo steering systems, wherein a steering wheel is forcibly coupled mechanically to the steerable vehicle wheels. The power assistance is so configured that actuators, e.g. hydraulic cylinders, are arranged in the mid-area of the steering mechanism. A force generated by means of the actuators assists the actuation of the steering mechanism in response to the rotation of the steering wheel. This arrangement reduces the force the driver has to exert during the steering maneuver.
Overriding steering systems are disclosed in DE 101 59 800 A1 and DE 101 59 700 A1, the contents of which are part of the application and on which the application is based. Said overriding steering systems are characterized in that it is possible for an actuator to superimpose another angle, if required, on the steering angle inputted by the driver. The additional angle is defined by a controller and used to enhance the stability and agility of the vehicle. It is also feasible to compensate disturbances and to realize the gradient wheel steering angle by way of the steering wheel angle as a function of the driving speed of the vehicle. Hydraulic or electric actuators are used.